Increasingly stringent legal requirements in respect of permissible pollutant emissions from motor vehicles powered by internal combustion engines make it necessary to minimize the pollutant emissions during operation of the internal combustion engine. This can be achieved on the one hand by reducing the pollutant emissions produced during combustion of the air/fuel mixture in the relevant cylinder of the internal combustion engine. On the other hand, exhaust after-treatment systems are used in internal combustion engines to convert the pollutant emissions produced during the combustion process of the air/fuel mixture in the relevant cylinder into harmless substances. For this purpose, catalytic converters are used which convert the carbon monoxide, hydrocarbons and nitrogen oxides into harmless substances. Selectively controlling the generation of the pollutant emissions during combustion and converting the pollutants with a high degree of efficiency by means of the catalytic converter both require a very precisely adjusted air/fuel ratio in the relevant cylinder.
In this context it must be ensured that the components of the exhaust after-treatment system operate in the desired manner over a long service life and faults are reliably detected.